Wireless communication apparatus and wireless communication method

ABSTRACT

A wireless communication apparatus having a relay function comprises a memory to store an address of a first wireless communication apparatus connected to the wireless communication apparatus and having a relay function, and a transmitting unit configured to transmit a first relay frame addressed to the first wireless communication apparatus, the first relay frame including a first address field prepared for a final destination address, an address of a second communication apparatus not connected to the wireless communication apparatus being set in the first address field, and a second address field prepared for an address of a third wireless communication apparatus connecting the second communication apparatus and having a relay function, one of an address except for the address of the third wireless communication apparatus and a specific value being set in the second address field.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2007-175568, filed Jul. 3, 2007,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to multi-hop communication that forwardsdata to a wireless communication apparatus via wireless relaycommunication apparatuses.

2. Description of the Related Art

When a wireless communication terminal for performing conventional relay(to be referred to as a wireless relay communication terminalhereinafter) relays data, the address of a final wireless relaycommunication terminal in a relay system is described in an addressfield of a frame to be transmitted, in addition to the address of awireless relay communication terminal as the direct transmissiondestination of the frame (e.g., Japanese Patent Nos. 3774426 and3774469, and W. Steven Conner et al., “IEEE802.11s Tutorial, Overview ofthe Amendment for Wireless Local Area Mesh Networking,” [online, IEEE802Meeting Tutorial Reference], Nov. 13, 2006, IEEE802, Internet <URL:http://www.ieee802.org/802_tutorials/index.htm “Tutorial #1 (6:30pm):802.11s:WLAN Mesh Networking”>). A method is described by which ifno routing information has been established when transmitting the frameto the final wireless relay communication terminal, a broadcast addressis set in the field for the address of the wireless relay communicationterminal as the direct transmission destination, thereby delivering theframe to the final wireless relay communication terminal (e.g., JapanesePatent No. 3774426 or 3774469).

There is also a method of relaying forwarding data by encapsulating suchdata (e.g., JP-A. 2006-279168 (KOKAI)), and a method of adding anaddress on a relay route to a frame header (e.g., JP-A. No. 2006-140943(KOKAI)).

Unfortunately, the above-mentioned conventional techniques are based onthe assumption that the final wireless relay terminal is determined, andhence cannot relay data if the terminal is undetermined. Also, none ofthe conventional techniques describe a method of controlling data relayin a situation in which a communication terminal connecting to the finalwireless relay communication terminal is the final destination terminalof data, and the final wireless relay communication terminal is changedbecause, e.g., the destination address terminal also connects to anotherwireless relay communication terminal. If a wireless relay communicationterminal that is in power save mode exists, it is difficult to expectthat routing information will be properly updated in the wireless relaysystem. Accordingly, the wireless relay will not function in the realsystem.

BRIEF SUMMARY OF THE INVENTION

According to embodiments of the present invention, a wirelesscommunication apparatus having a relay function stores, in a memory,addresses of a plurality of other wireless communication apparatusesincluding a first wireless communication apparatus connected to thewireless communication apparatus and having a relay function;

transmits a first relay frame addressed to the first wirelesscommunication apparatus, the first relay frame including (a) a firstaddress field prepared for describing a final destination address, anaddress of a second communication apparatus not connected to thewireless communication apparatus being described in the first addressfield, and (b) a second address field prepared for describing an addressof a third wireless communication apparatus connecting the secondcommunication apparatus and having a relay function, one of an addressexcept for the address of the third wireless communication apparatus anda specific value being described in the second address field, when theaddress of the third wireless communication apparatus is not stored inthe memory; and

transmits, when the address of the third wireless communicationapparatus is stored in the memory, a second relay frame including (a)the first address field in which the address of the second communicationapparatus is described, and (b) the second address field in which theaddress of the third wireless communication apparatus is described.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a view showing an example of the configuration of a wirelesscommunication system according to embodiments of the present inventionwhen relaying data between wireless communication terminals;

FIG. 2 is a view showing an example of the arrangement of a wirelesscommunication terminal having a wireless relay function (i.e. wirelessrelay communication terminal);

FIGS. 3A to 3D are views showing practical examples of an address table;

FIG. 4 is a view showing an example of the arrangement of a MAC dataframe;

FIG. 5 is a view showing an example of the arrangement of a FrameControl field in a MAC header;

FIG. 6 is a view showing an example of the arrangement of a Relay Headerfield in the MAC header;

FIG. 7 is a view showing a method of using address fields;

FIG. 8 is a flowchart for explaining the operation of a wireless relaycommunication terminal according to the first embodiment;

FIG. 9 is a flowchart for explaining the operation of a wireless relaycommunication terminal according to the second embodiment;

FIG. 10 is a view showing an example of the use of the address fieldswhen a final wireless relay communication terminal is determined;

FIG. 11 is a view showing an example of the use of the address fieldswhen a final wireless relay communication terminal is undetermined;

FIG. 12 is a flowchart for explaining the operation of a wireless relaycommunication terminal according to the third embodiment;

FIG. 13 is a view for explaining the case where it is necessary tocorrect the address of a final wireless relay communication terminal;

FIG. 14 is a view showing a practical example of the address fields ofthe MAC header in which the address of the final wireless relaycommunication terminal is corrected;

FIG. 15 is a flowchart for explaining the operation of a wireless relaycommunication terminal according to the fourth embodiment;

FIG. 16 is a flowchart for explaining the operation of a wireless relaycommunication terminal according to the fifth embodiment;

FIG. 17 is a flowchart for explaining another operation of the wirelessrelay communication terminal according to the fifth embodiment;

FIG. 18 is a flowchart for explaining another operation of the wirelessrelay communication terminal according to the fifth embodiment;

FIG. 19 is a flowchart for explaining another operation of the wirelessrelay communication terminal according to the fifth embodiment;

FIG. 20 is a flowchart for explaining another operation of the wirelessrelay communication terminal according to the fifth embodiment;

FIG. 21 is a flowchart for explaining another operation of the wirelessrelay communication terminal according to the fifth embodiment; and

FIG. 22 is a view for explaining the address of a wireless communicationterminal.

DETAILED DESCRIPTION OF THE INVENTION

In the system shown in FIG. 1, wireless communication terminals 201,202, 203, and 204 having a wireless relay function (wireless relaycommunication terminals) are connected. The wireless relay communicationterminal may also connect to a plurality of wireless relay communicationterminals or to a plurality of wireless communication terminals or wiredcommunication terminals having no wireless relay function. Referring toFIG. 1, the wireless relay communication terminal 201 is connected towireless communication terminals 101 and 102 having no wireless relayfunction, and the wireless relay communication terminal 203 is connectedto a wireless communication terminal 103 having no wireless relayfunction. The wireless relay communication terminal 202 is not connectedto any wireless communication terminal having no wireless relayfunction, and the wireless relay communication terminal 204 is connectedto a communication terminal 301 through wire (wired communicationterminal).

A wireless relay communication terminal and wireless communicationterminals connecting to the wireless relay communication terminal andhaving no wireless relay function correspond to the infrastructure BSS(Basic Service Set) configured by units called a wireless base stationand wireless communication terminals in the IEEE802.11 wireless LANsystem. Any wireless relay communication terminal may and may notconnect to a wireless communication terminal having no wireless relayfunction, and need not connect to any communication terminal throughwire. A wireless communication terminal connecting to a wireless relaycommunication terminal and having no wireless communication functionneed not only perform wireless communication with the wireless relaycommunication terminal, but may also perform wireless communication witha wireless communication terminal connecting to the wireless relaycommunication terminal and having no wireless relay function.

A communication form that performs wireless data relay is calledwireless relay communication or multi-hop communication, and a systemconsisting of such kind of wireless communication is called a wirelessrelay system or multi-hop communication system. Data is converted into aframe corresponding to the wireless communication method, andtransmitted to another wireless communication terminal connected bywireless communication. An example of the data is data forwarded fromthe Logical Link Control (LLC) layer as the upper layer of the MAC(Media Access Control) layer in the IEEE802.11 wireless LAN system, andinserted as a payload or Frame Body field into the frame.

For example, when transmitting data from the wireless communicationterminal 101 to the communication terminal 301 in FIG. 1, the wirelesscommunication terminal 101 converts the data into a frame and transmitsthe frame to the wireless relay communication terminal 201. The wirelessrelay communication terminal 201 converts the received frame into aframe addressed to the wireless relay communication terminal 202, andtransmits the frame. The wireless relay communication terminal 202converts the received frame into a frame addressed to the wireless relaycommunication terminal 203, and transmits the frame. The wireless relaycommunication terminal 203 converts the received frame into a frameaddressed to the wireless relay communication terminal 204, andtransmits the frame. In this case, the wireless communication terminal101 is the generation source of the frame, and the communicationterminal 301 is the final destination terminal of the frame. Also, thewireless relay communication terminal 204 is the final relay wirelesscommunication terminal. The function of the wireless relay communicationterminal which converts a received frame into a frame directed to thenext communication terminal and transmits the frame is called a relayfunction or forwarding function.

Although the case where the wireless communication terminal 101transmits data to the communication terminal 301 has been explainedabove, the wireless relay communication terminal 204, for example, mayalso be the final destination terminal of the frame. In this case, thefinal wireless relay communication terminal and the final destinationterminal are the same. Likewise, the wireless communication terminal103, for example, may also be the final destination (wireless) terminalof the frame, in which case the wireless relay communication terminal203 is the final wireless relay communication terminal.

FIG. 2 shows an example of the arrangement of the main parts of thewireless relay communication terminal. Referring to FIG. 2, the wirelessrelay communication terminal includes an antenna 10, a receiver 11, atransmitter 12, a transmission/reception controller 13, an address tablestorage unit 14, and a timer 15. Note that when the wireless relaycommunication terminal has a function of connecting to the communicationterminal 301 through wire like the wireless relay communication terminal204 shown in FIG. 1, the wireless relay communication terminal furtherincludes a wired communication functional unit connected to thetransmission/reception controller 13.

The receiver 11 performs, e.g., frequency conversion, conversion from ananalog signal to a digital signal, and demodulation on a signal receivedby the antenna 10, and outputs the signal to the transmission/receptioncontroller 13. The transmitter 12 performs, e.g., modulation, conversionfrom a digital signal to an analog signal, and frequency conversion onan input signal from the transmission/reception controller 13, andtransmits the signal from the antenna 10.

The transmission/reception controller 13 incorporates a memory forproviding a work area, frame buffer, and the like, and conforms to,e.g., the IEEE802.11 wireless LAN (including wireless LANs correspondingto a series of amended/extended standards of IEEE802.11 such as 802.11a,802.11b, 802.11e, 802.11g, 802.11h, 802.11i, and 802.11j) system. Thetransmission/reception controller 13 performs an operation defined forthe MAC layer and an operation defined for the PHY (physical) layer.

As the defined MAC layer operation, the transmission/receptioncontroller 13 performs, e.g., MAC header processing, access control inframe transmission, received frame processing including response frametransmission, and management related to the settings between wirelesscommunication terminals. The transmission/reception controller 13 alsoperforms a process of receiving data to be transmitted from the upperlayer of the MAC layer, and forwarding received data to the upper layerof the MAC layer if the final destination of the data is its ownterminal.

As the defined PHY layer operation, the transmission/receptioncontroller 13 performs, e.g., PLCP (Physical Layer Convergence Protocol)header processing.

The address table storage unit 14 stores an address table registeringrouting information. A wireless relay communication terminal uses therouting information in a relay process for forwarding data to anotherwireless communication terminal. Note that this address table need notstore routing information for relaying data to all communicationterminals. Note also that the transmission/reception controller 13 mayinclude the address table storage unit 14.

As shown in FIGS. 3A to 3D, the address table registers, for the address(e.g., the MAC address) of each wireless relay communication terminal,the address (e.g., the MAC address) of a terminal connected to thewireless relay communication terminal. For example, FIG. 3A shows anaddress table corresponding to the first BSS that the wireless relaycommunication terminal 201 belongs to, FIG. 3B shows an address tablecorresponding to the second BSS that the wireless relay communicationterminal 203 belongs to, and FIG. 3C shows an address tablecorresponding to the third BSS that the wireless relay communicationterminal 204 belongs to.

Note that in the following explanation, the addresses (MAC addresses) ofthe wireless relay communication terminals 201 to 204 will be denoted by“201” to “204” by directly using their reference numerals, and theaddresses (MAC addresses) of the terminals 101 to 103 and 301 will bedenoted by “101” to “103” and “301” by directly using their referencenumerals. Note also that the addresses (MAC addresses) of the wirelessrelay communication terminals 201 to 204 will be used as the identifiers(BSSIDs) of the BSSs to which these wireless relay communicationterminals belong.

The address table storage unit 14 of each wireless relay communicationterminal stores an address table registering the MAC addresses ofwireless communication terminals (including wireless relay communicationterminals) connected to the wireless relay communication terminal. Forexample, as shown in FIG. 3A, the address table storage unit 14 of thewireless relay communication terminal 201 stores an address tableregistering the MAC addresses of the wireless communication terminals101 and 102 and the wireless relay communication terminal 202 connectedto the wireless relay communication terminal 201. Likewise, as shown inFIG. 3B, the address table storage unit 14 of the wireless relaycommunication terminal 203 stores an address table registering the MACaddresses of the wireless communication terminal 103 and the wirelessrelay communication terminals 202 and 204 connected to the wirelessrelay communication terminal 203. Also, as shown in FIG. 3C, the addresstable storage unit 14 of the wireless relay communication terminal 204stores an address table registering the MAC addresses of thecommunication terminal 301 and the wireless relay communication terminal203 connected to the wireless relay communication terminal 204.

Furthermore, as shown in FIG. 3D, the address table storage unit 14 ofthe wireless relay communication terminal 202 stores an address tableregistering the MAC addresses of the wireless relay communicationterminals 201 and 203 connected to the wireless relay communicationterminal 202, the address table as shown in FIG. 3A received from thewireless relay communication terminal 201 when the wireless relaycommunication terminal 202 is connected to the wireless relaycommunication terminal 201, and the address table as shown in FIG. 3Breceived from the wireless relay communication terminal 203 when thewireless relay communication terminal 202 is connected to the wirelessrelay communication terminal 203. That is, the MAC addresses of thewireless relay communication terminals 201 and 203 connected to thewireless relay communication terminal 202 are also registered in the“BSSID” field of the address table shown in FIG. 3D, and the MACaddresses of the wireless communication terminals 101 and 102 and thewireless relay communication terminal 202 connected to the wirelessrelay communication terminal 201 and the MAC addresses of the wirelesscommunication terminal 103 and the wireless relay communicationterminals 202 and 204 connected to the wireless relay communicationterminal 203 are registered in the “connected terminal” field of theaddress table shown in FIG. 3D. This address table may also includeinformation indicating which communication terminal has a relay function(which communication terminal is a wireless relay communicationterminal), in addition to the address of the terminal. Note that inFIGS. 3A to 3D, “R” is prefixed to the address of each wireless relaycommunication terminal to indicate that the address represents awireless relay communication terminal.

As described above, each wireless relay communication terminal can alsoexchange address tables with another wireless relay communicationterminal when connected to it.

Note that the address tables as shown in FIGS. 3A to 3D show wirelesscommunication terminals (including wireless relay communicationterminals) connected to each relay communication apparatus, and a routeto a target wireless communication terminal (including a wireless relaycommunication terminal) can be found by tracing this connectionrelationship. Therefore, the information registered in the address tableis also called routing information.

All the wireless relay communication terminals 201 to 204 shown in FIG.1 can find out wireless communication terminals (including wirelessrelay communication terminals) connected to each wireless relaycommunication terminal by exchanging the address tables with each other.In this case, the wireless relay communication terminal 201 can find outthat the wireless relay communication terminal 204 is connected to thewireless relay communication terminal 203, and the communicationterminal 301 is connected to the wireless relay communication terminal204. However, it is sometimes impossible to obtain the address tables ofsome wireless relay communication terminals for some reason. Forexample, if only the information as shown in FIG. 3A is stored in theaddress table storage unit 14 of the wireless relay communicationterminal 201, the wireless relay communication terminal 201 cannot findout that the wireless relay communication terminal 204 and the wirelesscommunication terminal 103 are connected to the wireless relaycommunication terminal 203, and that the communication terminal 301 isconnected to the wireless relay communication terminal 204.

Multi-hop communication methods for a case like this will be explainedin the following embodiments.

FIRST EMBODIMENT

FIG. 4 is a view showing an example of the arrangement of a MAC dataframe according to the first embodiment. A portion from a Frame Controlfield to a Relay Header field before a Frame Body field in FIG. 4 is aMAC header portion. Data generated in the LLC layer as the upper layerof the MAC layer is inserted into the Frame Body field in, e.g., theIEEE802.11 wireless LAN system. Fields such as a QoS Control field to beused when performing QoS control may also be added to the MAC headerportion in addition to the fields shown in FIG. 4.

FIG. 5 illustrates the format of the Frame Control field shown in FIG.4. FIG. 6 illustrates the format of the Relay Header field shown in FIG.4.

The types of MAC frames to be transmitted in the IEEE802.11 wireless LANsystem are a data frame for transmitting data generated in the upperlayer of the MAC layer, a management frame for transmitting MAC layerlevel management information, and a control frame related to MAC layeraccess control.

The structure of the data frame is a versatile one including thestructures of the management frame and the control frame. The managementframe and the control frame use part of the fields shown in FIG. 4.

In the data frame, the fields in the MAC header portion are selectivelyused in accordance with the status of transmission as shown in FIG. 7. AToDS field and a FromDS field exist in the Frame Control field shown inFIG. 5. The ToDS field is set to “1” when the direct transmissiondestination of a transmission frame is a wireless base station or awireless relay communication terminal, and set to “0” in other cases.The FromDS field is set to “1” when the direct transmission source of atransmission frame is a wireless base station or wireless relaycommunication terminal, and set to “0” in other cases.

An AE (Address Extension) field exists in the Relay Header field shownin FIG. 6. The AE field is set to “1” when an Address 5 field and anAddress 6 field in the Relay Header field are added, and set to “0” inother cases. The Relay Header field itself is a field added whenperforming wireless relay communication. The AE field can be set to “1”only when ToDS=1 and FromDS=1. Note that it is not always necessary tohave this format with the AE field in the Relay Header, and it issufficient if the addition of the Address 5 field and the Address 6field to the MAC header portion can be indicated. For example, theaddition of the Address 5 field and the Address 6 field can be indicatedby a transmission frame type indicated by a Type or Subtype field in theFrame Control field or a specific value in another field (or by acombination of fields), or by detecting the capability of a terminalhaving transmitted the frame. For example, the existence of the RelayHeader field is detected when a terminal receiving a frame is a wirelessrelay communication terminal and the transmission source terminal of theframe is a wireless relay communication terminal.

A row e in FIG. 7 shows an example in which when ToDS=1, FromDS=1, andAE=1, i.e., the Address 5 field and the Address 6 field are added, aRelay DA, a Relay SA, a DA, and an SA are respectively inserted intoAddress 3, Address 4, Address 5, and Address 6 fields. However, it isalso possible to respectively insert the DA and the SA in Address 3 andAddress 4 fields, in the same manner as when TODS=1, FromDS=1, and AE=0,i.e., the Address 5 field and the Address 6 field are not added, andrespectively insert the Relay DA and the Relay SA necessary for wirelessrelay communication in Address 5 and Address 6 fields which are added.Values to be inserted into the individual address fields shown here,i.e., the DA, the SA, the Relay DA, and the Relay SA, and an RA and a TAwill be described later.

Data frames related to a wireless relay communication terminal on awireless relay communication system are the cases where ToDS=0 andFromDS=1, ToDS=1 and FromDS=0, and ToDS=1 and FromDS=1 (AE=0 or 1).

For example, the existence of the Relay Header field is indicated by thetype of transmission frame indicated by the Type or Subtype field in theFrame Control field or by a specific value in another field (or by acombination of fields). Alternatively, the existence of the Relay Headerfield is found by detecting the capability of a terminal thattransmitted the frame.

A data frame in which TODS=0 and FromDS=0 shown in a row a in FIG. 7 isexchanged between wireless communication terminals that are not basestations nor wireless rely communication terminals, i.e., wirelesscommunication terminals that have no rely function. This data frame isused when the wireless communication terminals 101 and 102 shown in FIG.1 perform wireless communication, or when wireless communication isperformed in a wireless communication form in which no wireless basestation exists (Independent Basic Service Set (IBSS) of IEEE802.11). AnAddress 1 field contains the direct transmission destination address(Receiver Address: RA) of a frame. Since no relay communication isperformed in this case, the RA is equivalent to the final destinationaddress (Destination Address: DA) of the frame. An Address 2 fieldcontains the direct transmission source address (Transmitter Address:TA) of the frame. Since no relay communication is performed, the TA isequivalent to the generation source address (Source Address: SA) of theframe. A BSS identifier (BSS Identification: BSSID) is inserted into anAddress 3 field. The BSSID is the MAC address of a wireless base stationin the infrastructure BSS described previously. For example, in the BSScomprising the wireless relay communication terminal 201 and thewireless communication terminals 101 and 102, BSSID of the BSS is theMAC address of the wireless relay communication terminal 201. In thiscase, an Address 4 field is not used (Not Available: N/A). Since noRelay Header field exists, the Address 5 field and the Address 6 fielddo not exist either (Not Present: N/P). It is not particularly necessaryto distinguish between N/A and N/P because there is no field.

A data frame in which ToDS=0 and FromDS=1 shown in a row b in FIG. 7 istransmitted from a wireless base station/wireless relay communicationterminal to a wireless communication terminal that is not base stationnor wireless rely communication terminal, i.e., wireless communicationterminal that has no rely function. For example, this data frame is usedwhen the wireless relay communication terminal 201 transmits a dataframe to the wireless communication terminal 101 or 102, or when thewireless relay communication terminal 203 transmits a data frame to thewireless communication terminal 103. The Address 1 field contains theRA. As in the case where ToDS=0 and FromDS=0 described above, the RA isequivalent to the DA because the frame is transmitted to a wirelesscommunication terminal (having no relay function) of a non-basestation/non-wireless relay communication terminal. The Address 2 fieldcontains the TA. Since the data frame is transmitted from a wirelessbase station/wireless relay communication terminal, the TA is equivalentto the MAC address of the wireless base station/wireless relaycommunication terminal, i.e., the BSSID. The Address 3 field containsthe SA. The SA is not necessarily the same as the BSSID because there isalso a case when the wireless base station/wireless relay communicationterminal transmits a data frame received from another wirelesscommunication terminal. For example, when the wireless communicationterminal 101 shown in FIG. 1 is the transmission source of data andtransmits the data to the wireless communication terminal 103 connectingto the wireless relay communication terminal 203, the data frame istransmitted from the wireless relay communication terminal 203 to thewireless communication terminal 103 via the wireless relay communicationterminals 201 and 202. In the transmission from the wireless relaycommunication terminal 203 to the wireless communication terminal 103, adata frame in which TODS=0 and FromDS=1 is used, and the SA is the MACaddress of the wireless communication terminal 101. The Address 4 fieldis not used (Not Available: N/A). Since no Relay Header field exists,the Address 5 field and the Address 6 field do not exist either (NotPresent: N/P).

A data frame in which ToDS=1 and FromDS=0 shown in a row c in FIG. 7 istransmitted from a wireless communication terminal that is not basestation nor wireless rely communication terminal, i.e., wirelesscommunication terminal that has no rely function to a wireless basestation/wireless relay communication terminal. This data frame is usedwhen the wireless communication terminal 101 or 102 transmits a dataframe to the wireless relay communication terminal 201 or the wirelesscommunication terminal 103 transmits a data frame to the wireless relaycommunication terminal 203 in FIG. 1. The Address 1 field contains theRA. Since the data frame is transmitted to a wireless basestation/wireless relay communication terminal in this case, the RA isequivalent to the MAC address of the wireless base station/wirelessrelay communication terminal, i.e., the BSSID. The Address 2 fieldcontains the TA. The TA is equivalent to the SA because the data frameis transmitted from a wireless communication terminal of a non-basestation/non-wireless relay communication terminal. The Address 3 fieldcontains the DA. The DA may be different from the BSSID because the dataframe may be further transmitted to another wireless basestation/wireless relay communication terminal. This data frame is usedas a data frame which, for example, the wireless communication terminal101 shown in FIG. 1 transmits to the wireless relay communicationterminal 201 when the data to the wireless communication terminal 103 isgenerated at the wireless communication terminal 101. In this case, theDA is the MAC address of the wireless communication terminal 103. TheAddress 4 field is not used (Not Available: N/A) in this case as well.Since no Relay Header field exists, the Address 5 field and the Address6 field do not exist either (Not Present: N/P).

A data frame in which TODS=1 and FromDS=1 shown in a row d in FIG. 7 istransmitted from a wireless base station/wireless relay communicationterminal to a wireless base station/wireless relay communicationterminal. If no Relay Header field exists or the AE field in the RelayHeader field is “0”, the Address 1 field, the Address 2 field, theAddress 3 field, and the Address 4 field respectively contain the RA,the TA, the DA, and the SA. This form is used when wireless relay can beexecuted by the same wireless system. When a wireless communicationterminal 104 connecting to the wireless relay communication terminal 202and having no relay function is added to FIG. 1 and the wirelesscommunication terminal 101 generates data and transmits it to thewireless communication terminal 104, the wireless relay communicationterminal 201 transmits the data frame shown in the row d in FIG. 7 tothe wireless relay communication terminal 202. In this case, the RA isthe MAC address of the wireless relay communication terminal 202, the TAis the MAC address of the wireless relay communication terminal 201, theDA is the MAC address of the wireless communication terminal 104, andthe SA is the MAC address of the wireless communication terminal 101. Ifthe Relay Header exists and the AE field in the Relay Header is “1”, theAddress 1 field and the Address 2 field similarly respectively containthe RA and the TA. However, the Address 3 field contains the address(Relay DA) of a final wireless relay communication terminal in thewireless relay system, and the Address 4 field contains the address(Relay SA) of a wireless relay communication terminal as the forwardingstarting point (generation source) of a relay frame in the wirelessrelay system. The added Address 5 and Address 6 fields respectivelycontain the DA and the SA. This data frame is used when transmittingdata to a final destination terminal not configured by the same wirelesssystem.

When transmitting data generated by the wireless communication terminal101 to the communication terminal 301 in FIG. 1, for example, the RA,the TA, the Relay SA, and the SA in a data frame which the wirelessrelay communication terminal 201 transmits to the wireless relaycommunication terminal 202 are respectively the MAC addresses of thewireless relay communication terminal 202, the wireless relaycommunication terminal 201, the wireless relay communication terminal201, and the wireless communication terminal 101. The Relay DA is theMAC address of the wireless relay communication terminal 204, and the DAis the MAC address of the communication terminal 301. Also, in a dataframe which the wireless relay communication terminal 202 transmits tothe wireless relay communication terminal 203, the RA is the MAC addressof the wireless relay communication terminal 203, the TA is the MACaddress of the wireless relay communication terminal 202, and the RelayDA, the Relay SA, the DA, and the SA respectively remain the same as theMAC addresses of the wireless relay communication terminal 204, thewireless relay communication terminal 201, the communication terminal301, and the wireless communication terminal 101. In a data frame whichthe wireless relay communication terminal 203 transmits to the wirelessrelay communication terminal 204, the RA is the MAC address of thewireless relay communication terminal 204, the TA is the MAC address ofthe wireless relay communication terminal 203, and the Relay DA, theRelay SA, the DA, and the SA respectively remain the same as the MACaddresses of the wireless relay communication terminal 204, the wirelessrelay communication terminal 201, the communication terminal 301, andthe wireless communication terminal 101.

Note that the form of AE=1 can also be taken even when wireless relaycan be executed by the same wireless system. In this case, whentransmitting data generated by the wireless communication terminal 101to the wireless communication terminal 103 in FIG. 1, for example, theRA is the MAC address of the wireless relay communication terminal 202,the TA is the MAC address of the wireless relay communication terminal201, the Relay DA is the MAC address of the wireless relay communicationterminal 203, the Relay SA is the MAC address of the wireless relaycommunication terminal 201, the DA is the MAC address of the wirelesscommunication terminal 103, and the SA is the MAC address of thewireless communication terminal 101, in a data frame which the wirelessrelay communication terminal 201 transmits to the wireless relaycommunication terminal 202.

When the address fields are allocated as shown in the row d in FIG. 7 byusing the AE field as described above, data relay between wireless relaycommunication terminals and communication between a wireless relaycommunication terminal and a communication terminal connecting to thewireless relay communication terminal and having no relay function arehierarchically separated. The addresses of wireless relay communicationterminals participating in data relay between wireless relaycommunication terminals are inserted into the first half of the addressfields which are from Address 1 to Address 4 fields, and the addressesof communication terminals related to the data and having no relayfunction are inserted into the second half of the address fields whichare Address 5 and Address 6 fields added by extension.

When AE=1, the address of a final wireless relay communication terminalis inserted into the Address 3 field. However, an appropriate addresscannot be set if the address of the final wireless relay communicationterminal is undetermined in a wireless relay communication terminal onthe route of data relay. In this case, therefore, the information in theAddress 1 field, i.e., the direct transmission destination address of arelay data frame is described in the Address 3 field.

FIG. 8 is a flowchart for explaining the operation of a wireless relaycommunication terminal according to the first embodiment. FIG. 8 showsthe operation of the transmission/reception controller 13 when thewireless relay communication terminal has received a frame or when thewireless relay communication terminal transmits internally generateddata.

When a wireless relay communication terminal has received a frameaddressed to the wireless relay communication terminal from anothercommunication terminal (e.g., when the wireless relay communicationterminal 201 has received a frame from the wireless communicationterminal 101 or 102 or from the wireless relay communication terminal202, when the wireless relay communication terminal 202 has received aframe from the wireless relay communication terminal 203 or 201, whenthe wireless relay communication terminal 203 has received a frame fromthe wireless relay communication terminal 202 or 204, or when thewireless relay communication terminal 204 has received a frame from thecommunication terminal 301 or wireless relay communication terminal 203in FIG. 1), i.e., when a wireless relay communication terminal hasreceived a frame in which the direct transmission destination address orRA contained in the Address 1 field (FIG. 4) is the wireless relaycommunication terminal, the process advances to step S1 related to arelay operation. In step S1, the process advances to step S2 because anobject frame is the received frame.

In step S2, whether internal data (frame body shown in FIG. 4) of thereceived frame is data to be forwarded is determined. In step S2, the DAof the received frame is checked. That is, the address described in theAddress 3 field is checked if AE=0 (if no Address 5 field is added inFIG. 6) as shown in the rows c and d in FIG. 7, and the addressdescribed in the Address 5 field is checked if AE=1 (if the Address 5field is added in FIG. 6) as shown in the row e in FIG. 7. If theaddress (the DA of the received frame) is not the MAC address of theterminal having received the frame, the data in the received frame isdata to be forwarded, so the process advances to step S3. If the addressis the MAC address of the terminal having received the frame, the datain the received frame is not data to be forwarded, so the processadvances to step S10 to terminate the processing.

“Forwarding” herein mentioned is to retransmit the received frame ontothe wireless medium (air), and means both transmission to anotherwireless relay communication terminal, and transmission to a wirelesscommunication terminal having no wireless relay function and connectingto the wireless relay communication terminal having received the frame.

In step S3, whether a wireless communication terminal at the finaldestination in the received frame is connected to the wireless relaycommunication terminal having received the frame is checked. In step S3,the wireless relay communication terminal refers to the address table(stored in the address table storage unit 14) registering the addressesof wireless communication terminals connected to the wireless relaycommunication terminal having received the frame, and checks whetherthere is the same address as the DA in the received frame among theaddresses of the wireless communication terminals (including wirelesscommunication terminals having no wireless relay function and thewireless relay communication terminals having a wireless relay function)connected to the wireless relay communication terminal having receivedthe frame. As described previously, the DA in the received frame is theaddress described in the Address 3 field when AE=0 as shown in the rowsc and d in FIG. 7 (when the Address 5 field shown in FIG. 6 is notadded), and the address described in the Address 5 field when AE=1 asshown in the row e in FIG. 7 (when the Address 5 field is added in FIG.6).

If it is determined in step S3 that the same address as the DA in thereceived frame is registered in the address table as the address of awireless communication terminal (a wireless communication terminalhaving no wireless relay function or a wireless relay communicationterminal) connected to the wireless relay communication terminal havingreceived the frame, i.e., that the wireless communication terminal atthe final destination in the received frame is connected to the wirelessrelay communication terminal having received the frame, the processadvances to step S8.

In step S8, a MAC header not using (not including) the Relay Headerfield shown in FIG. 4 is generated, and the process advances to awireless transmission process in step S9.

This MAC header not using (not including) the Relay Header field shownin FIG. 4 is called a non-relay frame MAC header. If the finaldestination is a wireless communication terminal having no wirelessrelay function and connecting to the wireless relay communicationterminal having received the frame, the non-relay frame MAC header isthe case where TODS=0 and FromDS=1 as shown in the row b in FIG. 7. Ifthe final destination is another wireless relay communication terminalconnecting to the wireless relay communication terminal having receivedthe frame, the non-relay frame MAC header is the case where TODS=1,FromDS=1, and AE=0 as shown in the row d in FIG. 7.

In step S9, a frame as shown in FIG. 4 is generated by adding the FrameBody field included in the received frame and an FCS (Frame CheckSequence) field to the MAC header portion in, e.g., the IEEE802.11wireless LAN system. Then, a series of transmission processes oftransmitting the generated frame through the acquisition of the wirelessmedium (channel access) and the like are performed.

Assume that normal receiving processes performed when a frame isreceived are already executed before step S1 or after step S10. Examplesof the processes are the setting of virtual carrier sense (NetworkAllocation Vector: NAV) in the IEEE802.11 wireless LAN, and the processof extracting data (the Frame Body portion shown in FIG. 4) from a framewhose final destination is a terminal having received the frame, andforwarding the data from the MAC layer to the upper layer such as theLogical Link Control (LLC) layer. Assume also that even when the frameis an object of not wireless forwarding but wired forwarding, theseprocesses are already executed before step S1 or after step S10. This isthe case where, for example, the wireless relay communication terminal204 shown in FIG. 1 forwards data to the communication terminal 301.Note that the routing information stored in the address table storageunit 14 may also be used in this forwarding through wire as well.

If it is determined in step S3 that the same address as the DA of thereceived frame is not registered in the address table as the address ofa wireless communication terminal (a wireless communication terminalhaving no wireless relay function or a wireless relay communicationterminal) connecting to the wireless relay communication terminal havingreceived the frame, i.e., that the wireless communication terminal atthe final destination DA in the received frame is not connected to thewireless relay communication terminal having received the frame, theprocess advances to step S4 to start a process of relaying the receivedframe, i.e., a relay frame transmission process.

In step S4, whether a final wireless relay communication terminal can bedetermined (whether search for the route to the DA is completed or thefinal wireless relay communication terminal is uniquely determined forthe DA) is checked. That is, in step S4, whether the routing information(the final destination DA, the address of the final wireless relaycommunication terminal connecting to the communication terminalcorresponding to the DA, and the addresses of wireless relaycommunication terminals existing (on the route) from the final wirelessrelay communication terminal to the wireless relay communicationterminal having received the frame) to the final destination, i.e., theDA, is registered in the address table is checked. If the final wirelessrelay communication terminal can be determined (if the routinginformation to the final destination (DA) is registered in the addresstable), the MAC address of the final wireless relay communicationterminal is adopted as the address to be inserted into the Address 3field (step S5). Then, the process advances to step S7 to generate a MACheader including the Relay Header field as shown in FIG. 4. In step S9,the wireless transmission process is performed.

The MAC header generated in step S7 is the case where ToDS=1, FromDS=1,and AE=1 as shown in the row e in FIG. 7.

If no final wireless relay communication terminal can be determined instep S4 (if the routing information to the final destination (DA) is notregistered in the address table 14), the process advances to step S6.

In step S6, from other wireless relay communication terminals registeredin the address table and connecting to the wireless relay communicationterminal having received the frame, the address of a wireless relaycommunication terminal as the direct transmission destination of therelay frame (RA), i.e., the address to be inserted into the Address 1field is selected and the same address is selected to be inserted in theAddress 3 field. In step S6, if the direct transmission source TA of theframe received in step S1 is a wireless relay communication terminal, awireless relay communication terminal except for the wireless relaycommunication terminal corresponding to the TA is selected from otherwireless relay communication terminals registered in the address tableand connecting to the wireless relay communication terminal havingreceived the frame. If a plurality of wireless relay communicationterminals are registered in the address table as the wireless relaycommunication terminals connecting to the wireless relay communicationterminal having received the frame, relay frames containing the samedata may be transmitted to those registered wireless relay communicationterminals. It is also possible to select a wireless relay communicationterminal as the transmission destination in accordance with anotherconventional method such as route search frame transmission.

In step S6 as described above, the RA to be inserted into the Address 1field is also adopted as the address to be inserted into the Address 3field.

Subsequently, the process advances to step S7 to generate a MAC headerincluding the Relay Header field as shown in FIG. 4, and advances to thewireless transmission process in step S9. In step S7, a MAC header asshown in the row e in FIG. 7 is generated. This is the case whereToDS=1, FromDS=1, and AE=1. Since no final relay terminal can bedetermined, the same MAC address as the MAC address (RA) in the Address1 field is inserted into the Address 3 field instead of the originalRelay DA.

If data is transferred from the upper layer to the MAC layer(transmission/reception controller 13) in the wireless relaycommunication terminal in step S1, the process advances to step S3 tostart a frame transmission process. This data can be data generated bythe upper layer or data received by the upper layer. An example is thecase where data from the communication terminal 301 is received by thewireless relay communication terminal 204 shown in FIG. 1 bycommunication through wire and forwarded to the MAC layer so as to betransmitted onto the wireless medium (by, e.g., the IEEE802.11 wirelessLAN system).

Processing from step S3 is the same as the above-mentioned process ofretransmitting the received frame onto the wireless medium. That is, ifit is determined in step S3 by referring to the address table that thewireless communication terminal at the final destination DA of thetransmission frame is connected to the wireless relay communicationterminal having received the frame, the process advances to step S8 togenerate a MAC header not including the Relay Header field shown in FIG.4, and then advances to the wireless transmission process in step S9. Ifit is determined in step S3 that the wireless communication terminal atthe final destination DA is not connected to the wireless relaycommunication terminal having received the frame, the process advancesto step S4 to start the process of relaying the received frame, i.e.,the relay frame transmission process.

In step S4, whether the routing information to the final destination,i.e., the DA, is registered in the address table is checked. If thefinal wireless relay communication terminal can be determined (if therouting information to the final destination (DA) is registered in theaddress table), this final wireless relay communication terminal isdetermined as the MAC address to be inserted into the Address 3 field(step S5). The process then advances to step S7 to generate a MAC headerincluding the Relay Header field as shown in FIG. 4. And then in stepS9, the wireless transmission process is performed.

If no final wireless relay communication terminal can be determined (ifno routing information to the final destination (DA) is registered inthe address table stored in the address table storage unit 14) in stepS4, the process advances to step S6. In step S6, from other wirelessrelay communication terminals registered in the address table andconnecting to the wireless relay communication terminal having receivedthe frame, the address of a wireless relay communication terminal as thedirect transmission destination of the transmission frame (RA), i.e.,the address to be inserted into the Address 1 field is selected and thesame address is selected to be inserted in the Address 3 field. In stepS7, a MAC header including the Relay Header field as shown in FIG. 4 isgenerated. The process then advances to the wireless transmissionprocess in step S9.

Note that this embodiment is not limited to the process sequence shownin the flowchart of FIG. 8. If the wireless relay communication terminalcannot determine the final wireless relay communication terminal, it isonly necessary to transmit a frame (relay frame) in which the MACaddress of a wireless relay communication terminal as the directtransmission destination (RA) is inserted into a field prepared toinsert the MAC address of the final wireless relay communicationterminal (Relay DA) (e.g., the Address 3 field shown in the row e inFIG. 7).

Note also that in the above first embodiment and in each of thefollowing embodiments, an address field prepared to describe the addressof the final wireless relay communication terminal is the Address 3field. However, the present invention is not limited to this case. Forexample, the address field prepared to describe the address of the finalwireless relay communication terminal may also be the Address 5 field orAddress 6 field. In this case, “Address 3 field” need only be replacedwith “Address 5 field” or “Address 6 field” in the explanation of theabove first embodiment or each of the following embodiments. This makesthe operation exactly the same as that when the address field preparedto describe the address of the final wireless relay communicationterminal is the Address 3 field.

(Effects)

In the above first embodiment, the MAC address of a wireless relaycommunication terminal as the direct transmission source of a relayframe (RA) is inserted into a field prepared to insert the address of afinal wireless relay communication terminal (e.g., the Address 3 fieldshown in the row e in FIG. 7). Accordingly, frame relay can be easilyperformed even in a situation in which the routing information to thefinal wireless relay communication terminal is undetermined(unregistered in the address table 14).

SECOND EMBODIMENT

In the second embodiment, when performing multi-hop communication, awireless relay communication terminal checks whether the address of thewireless relay communication terminal is set in an address field for theaddress of a final wireless relay communication terminal in a receivedframe.

FIG. 9 is a flowchart for explaining the operation of a wireless relaycommunication terminal according to the second embodiment. FIG. 9 showsthe operation of the transmission/reception controller 13 when thewireless relay communication terminal receives a frame and transmitsinternally generated data. Note that the same reference numerals as inFIG. 8 denote the same portions in FIG. 9, and different portions willbe mainly explained below.

FIG. 9 differs from FIG. 8 in that steps S21 and S22 are added afterstep S2. If it is determined in step S2 that the final destinationaddress (DA) of a received frame is not the MAC address of the terminalhaving received the frame, data in the received frame is data to beforwarded, so the process advances to step S21.

In step S21, whether the received frame includes the six address fields(the Address 1, 2, 3, and 4 fields in FIG. 4 and the Address 5 and 6fields in FIG. 6) is checked. For example, whether AE=1 in the RelayHeader field is checked. If AE=1, the received frame includes the sixaddress fields. If the received frame includes the six address fields,the process advances to step S22; if not, the process advances to stepS3.

In step S22, whether the address in the Address 3 field (the Relay DA inthe Address 3 field in the row e in FIG. 7) of the received frame is theaddress of the wireless relay communication terminal having received theframe is checked.

In this case, the direct transmission destination address (RA) containedin the Address 1 field (FIG. 4) of the received frame is the wirelessrelay communication terminal having received the frame (step S1). Also,if the address in the Address 3 field is the address of the wirelessrelay communication terminal having received the frame (step S22), thisis the case where ToDS=1, FromDS=1, and AE=1 in the row e in FIG. 7,indicating that the Address 1 field and the Address 3 field contain theMAC address of the wireless relay communication terminal having receivedthe frame.

If it is determined in step S2 that the data in the received frame isdata to be forwarded, whether the frame has the frame structure of arelay frame is checked in step S21. For example, if the wirelesscommunication terminal 101 transmits data whose final destination is thewireless communication terminal 103 to the wireless relay communicationterminal 201 in FIG. 1, the wireless relay communication terminal 201receives the frame in which TODS=1 and FromDS=0 shown in the row c inFIG. 7. Since this frame does not include the Address 5 field (and theAddress 6 field), the process advances to step S3. In step S3, it isdetermined that the DA in the Address 3 field is the address of thewireless communication terminal 103 and the wireless communicationterminal 103 is not directly connected to the wireless relaycommunication terminal 201, so the process advances to step S4. In stepS4, if the wireless relay communication terminal 201 can find out thatthe wireless communication terminal 103 is connected to the wirelessrelay communication terminal 203 from the address table stored in theaddress table storage unit 14 of the wireless relay communicationterminal 201, the wireless relay communication terminal 201 determinesthe address of the wireless relay communication terminal 203 as theaddress (Relay DA) of a final wireless relay communication terminal tobe inserted into the Address 3 field (step S5). Then, the processadvances to step S7.

In step S7, a MAC header having a configuration shown in a row a in FIG.10 is generated. That is, a relay frame in which ToDS=1, FromDS=1, AE=1,the MAC address of the wireless relay communication terminal 202 isinserted into the Address 1 field, the MAC address of the wireless relaycommunication terminal 201 is inserted into the Address 2 field, the MACaddress of the wireless relay communication terminal 203 is insertedinto the Address 3 field, the MAC address of the wireless relaycommunication terminal 201 is inserted into the Address 4 field, the MACaddress of the wireless communication terminal 103 is inserted into theAddress 5 field, and the MAC address of the wireless communicationterminal 101 is inserted into the Address 6 field is generated andtransmitted onto the wireless medium (step S9).

In step S4, if the wireless relay communication terminal 201 cannot findout that the wireless communication terminal 103 is connected to thewireless relay communication terminal 203 from the address table storedin the address table storage unit 14 of the wireless relay communicationterminal 201, the process advances to step S6.

In step S6, the MAC address of the wireless relay communication terminal202 directly connected to the wireless relay communication terminal 201is acquired from the address table, and selected as the address of thefinal wireless relay communication terminal, i.e., as the value of theAddress 3 field of the six address fields. After that, the processadvances to step S7.

In step S7, a MAC header having a configuration shown in a row a in FIG.11 is generated. That is, a relay frame in which ToDS=1, FromDS=1, AE=1,the MAC address of the wireless relay communication terminal 202 isinserted into the Address 1 field, the MAC address of the wireless relaycommunication terminal 201 is inserted into the Address 2 field, the MACaddress of the wireless relay communication terminal 202 is insertedinto the Address 3 field, the MAC address of the wireless relaycommunication terminal 201 is inserted into the Address 4 field, the MACaddress of the wireless communication terminal 103 is inserted into theAddress 5 field, and the MAC address of the wireless communicationterminal 101 is inserted into the Address 6 field is generated (step S7)and transmitted onto the wireless medium (step S9).

The wireless relay communication terminal 202 having received thetransmitted frame advances from step S1 to steps S2 and S21. Since it isdetermined in step S21 that the received frame includes the six addressfields, the process advances to step S22. If it is determined in stepS22 that the Address 3 field of the received frame does not contain theMAC address of the wireless relay communication terminal 202, theprocess advances to step S7. In this case, the MAC address designated inthe Address 3 field of the frame received in step S1 is directly adoptedin the Address 3 field of a relay frame generated in step S7.

In the above-mentioned example in which the wireless communicationterminal 101 transmits the data whose final destination is the wirelesscommunication terminal 103 to the wireless relay communication terminal201 in FIG. 1, if the wireless relay communication terminal 201transmits the relay frame as shown in the row a in FIG. 10, the MACaddress of the wireless relay communication terminal 203 described inthe Address 3 field is directly used in a relay frame transmitted by thewireless relay communication terminal 202 having received the formerrelay frame. That is, as shown in a row b in FIG. 10, in the relay frametransmitted by the wireless relay communication terminal 202, TODS=1,FromDS=1, AE=1, the Address 1 field contains the MAC address of thewireless relay communication terminal 203, the Address 2 field containsthe MAC address of the wireless relay communication terminal 202, theAddress 3 field contains the MAC address of the wireless relaycommunication terminal 203, the Address 4 field contains the MAC addressof the wireless relay communication terminal 201, the Address 5 fieldcontains the MAC address of the wireless communication terminal 103, andthe Address 6 field contains the MAC address of the wirelesscommunication terminal 101.

If it is determined in step S22 that the Address 3 field of the receivedframe contains the MAC address of the terminal having received theframe, the process advances to step S3. In the above-mentioned examplein which the wireless communication terminal 101 transmits the datawhose final destination is the wireless communication terminal 103 tothe wireless relay communication terminal 201 in FIG. 1, if the wirelessrelay communication terminal 201 transmits the relay frame as shown inthe row a in FIG. 11, the value described in the Address 3 field of therelay frame transmitted from the wireless relay communication terminal201 is the MAC address of the wireless relay communication terminal 202(step S22), so the process advances to step S3. Since the wirelesscommunication terminal 103 described in the Address 5 field is notdirectly connected to the wireless relay communication terminal 202(step S3), the process advances to step S4. In step S4, if the wirelessrelay communication terminal 202 can find out from the address tablestored in the address table storage unit 14 that the wirelesscommunication terminal 103 is connected to the wireless relaycommunication terminal 203, the process advances to steps S5 and S7. Arelay frame as shown in a row b in FIG. 11 in which ToDS=1, FromDS=1,AE=1, the Address 1 field contains the MAC address of the wireless relaycommunication terminal 203, the Address 2 field contains the MAC addressof the wireless relay communication terminal 202, the Address 3 fieldcontains the MAC address of the wireless relay communication terminal203, the Address 4 field contains the MAC address of the wireless relaycommunication terminal 201, the Address 5 field contains the MAC addressof the wireless communication terminal 103, and the Address 6 fieldcontains the MAC address of the wireless communication terminal 101 isgenerated and transmitted. In step S4, even if the wireless relaycommunication terminal 202 cannot find out from the address table storedin the address table storage unit 14 that the wireless communicationterminal 103 is connected to the wireless relay communication terminal203, the process advances to step S6 and the wireless relaycommunication terminal 202 selects the wireless relay communicationterminal 203 as the direct transmission destination address (RA) andselects the MAC address of the wireless relay communication terminal 203also as the MAC address of the Address 3 field. Then, the processadvances to step S7, resulting in the case shown in the row b in FIG.11.

Furthermore, if the wireless relay communication terminal 203 hasreceived the relay frame as shown in the rows b in FIGS. 10 and 11, thewireless relay communication terminal 203 advances from step S1 to stepsS2, S21, and S22. Since it is determined in step S22 that the Address 3field of the received frame contains the MAC address of the wirelessrelay communication terminal 203, the process advances to step S3.

In step S3, it is determined that the MAC address of the wirelesscommunication terminal 103 described in the Address 5 field isregistered in the address table stored in the address table storage unit14 of the wireless relay communication terminal 203, i.e., that thewireless communication terminal 103 is wirelessly connected to thewireless relay communication terminal 203, the process advances to stepS8.

In step S8, the MAC header shown in the row b in FIG. 7 is generated.That is, as shown in rows c in FIGS. 10 and 11, a non-relay frame MACheader in which ToDS=0, FromDS=1, the Address 1 field contains the MACaddress of the wireless communication terminal 103, the Address 2 fieldcontains the MAC address of the wireless relay communication terminal203, and the Address 3 field contains the MAC address of the wirelesscommunication terminal 101 extracted from the Address 6 field in thereceived relay frame shown in the rows b in FIGS. 10 and 11 isgenerated. In the generated non-relay frame MAC header, neither theAddress 5 field nor the Address 6 field exists, and the Address 4 fieldis N/A.

The non-relay frame generated in step S8 is transmitted onto thewireless medium through step S9.

In the above example, when the wireless communication terminal 101 shownin FIG. 1 transmits the data whose final destination is the wirelesscommunication terminal 103 to the wireless relay communication terminal201, the wireless relay communication terminal 201 (the first wirelessrelay communication terminal) cannot determine the final wireless relaycommunication terminal (e.g., the wireless relay communication terminal203 in this case). As shown in the row a in FIG. 11, therefore, theAddress 3 field of the relay frame contains the MAC address of thewireless relay communication terminal 202 connected to the wirelessrelay communication terminal 201. However, the wireless relaycommunication terminal 202 (the second wireless relay communicationterminal) having received this relay frame can determine the finalwireless relay communication terminal (wireless relay communicationterminal 203). As shown in the row b in FIG. 11, therefore, a relayframe in which the address in the Address 3 field is rewritten by theMAC address of the final wireless relay communication terminal (wirelessrelay communication terminal 203) is transmitted.

In the second embodiment as described above, when the second wirelessrelay communication terminal receives a relay frame which is transmittedfrom the first wireless relay communication terminal and in which theaddress of a final wireless relay communication terminal is not set inan address field for the address of a final wireless relay communicationterminal, and if the second wireless relay communication terminal candetermine the address of the final wireless relay communicationterminal, the second wireless relay communication terminal updates theaddress in this address field to the address of the final wireless relaycommunication terminal.

The process sequence is not limited to that shown in the flowchart ofFIG. 9, provided that the configuration as described above is achieved.

If the second wireless relay communication terminal can determine thefinal wireless relay communication terminal in step S4 through step S22shown in FIG. 9, the routing information (e.g., the final destinationDA, the address of the final wireless relay communication terminalconnecting a communication terminal corresponding to the DA, and theaddresses of wireless relay communication terminals existing from thefinal wireless relay communication terminal to the wireless relaycommunication terminal having received the frame, or at least theaddress of the final wireless relay communication terminal) to the finalwireless relay communication terminal stored in the address tablestorage unit 14 of the second wireless relay communication terminal mayalso be transmitted to the wireless relay communication terminal havingtransmitted the relay frame received in step S1 (i.e., the firstwireless relay communication terminal having failed to determine thefinal wireless relay communication terminal).

(Effects)

In the above second embodiment, if a wireless relay communicationterminal having received a frame determines that the address of thewireless relay communication terminal is set in a field (e.g., theAddress 3 field) prepared for the address of a final wireless relaycommunication terminal of the relay frame, and that a terminal at anaddress described in a field (e.g., the Address 1 field) prepared forthe address of a final destination terminal is not a terminal connectedto the wireless relay communication terminal, the wireless relaycommunication terminal updates the address in the above Address 3 field,if possible, by the address of the final wireless relay communicationterminal on the basis of relay information held in the wireless relaycommunication terminal, and transmits the relay frame. Accordingly, evenwhen the relay frame is transmitted while the routing information to thefinal destination is undetermined, frame relay can be continued to thefinal destination via the final wireless relay communication terminal.

Also, when a wireless relay communication terminal relays a frame afterextrapolating a field prepared for the final wireless relaycommunication terminal of the relay frame, the routing information(e.g., the final destination DA, the address of the final wireless relaycommunication terminal connecting a communication terminal correspondingto the DA, and the addresses of wireless relay communication terminalsexisting from the final wireless relay communication terminal to thewireless relay communication terminal having received the relay frame,or at least the address of the final wireless relay communicationterminal) used in the extrapolation is transmitted to a wireless relaycommunication terminal as the direct transmission source of the receivedrelay frame. This makes it possible to efficiently notify newer relayinformation to the wireless relay communication terminal as the directtransmission source of the relay frame. Consequently, the relay functioncan be implemented even in a situation in which a wireless relaycommunication terminal holding old routing information exists.

THIRD EMBODIMENT

FIG. 12 is a flowchart for explaining the operation of a wireless relaycommunication terminal according to the third embodiment. FIG. 12 showsthe operation of the transmission/reception controller 13 when thewireless relay communication terminal receives a frame and transmitsinternally generated data. Note that the same reference numerals as inFIGS. 8 and 9 denote the same portions in FIG. 12, and differentportions will be mainly explained.

FIG. 12 differs from FIG. 9 in that step S23 is added as processingperformed if an address field for the address of a final wireless relaycommunication terminal (e.g., the Address 3 field in this case) in areceived frame does not contain the address of the wireless relaycommunication terminal having received the frame (i.e., if NO in stepS22).

In step S23, whether to update the address of the final wireless relaycommunication terminal in the received relay frame is determined. If YESin step S23, the process advances to step S5 to determine the newaddress of the final wireless relay communication terminal as theaddress to be inserted into the Address 3 field. Then, the processadvances to step S7, and a relay frame MAC header is generated andtransmitted onto the wireless medium as described previously (step S9).

That is, even when the Address 3 field in the received relay framecontains the address of the final wireless relay communication terminal,if the contents of the address table of the wireless relay communicationterminal that transmitted this relay frame are old, this final wirelessrelay communication terminal address may have been changed to anotherfinal wireless relay communication terminal address. If this is the casein the third embodiment, the wireless relay communication terminal findsout that the address of the final wireless relay communication terminalin the received relay frame differs from the address of the finalwireless relay communication terminal obtained from the routinginformation held in the wireless relay communication terminal havingreceived the frame, and corrects the address to the new address.

Similarly to the second embodiment, the third embodiment will beexplained by taking the case where the wireless communication terminal101 transmits data whose final destination is the wireless communicationterminal 103 in FIG. 1 as an example. For example, when the wirelessrelay communication terminal 201 transmits the relay frame as shown inthe row a in FIG. 10, the wireless relay communication terminal 202having received this relay frame determines in step S23 whether toupdate the MAC address of the wireless relay communication terminal 203described in the Address 3 field of the relay frame.

In step S23, the wireless relay communication terminal 202 firstextracts the address of a final relay terminal (Relay DA) from, e.g.,the Address 3 field of the received relay frame, and extracts theaddress of a final destination terminal (DA) from, e.g., the Address 5field. In this case, the MAC address of the wireless communicationterminal 103 is extracted as the DA. If the address of a wireless relaycommunication terminal (e.g., the wireless relay communication terminal203 in this case) connected to the wireless communication terminal 103as the DA is registered in the address table stored in the address tablestorage unit 14 of the wireless relay communication terminal 202, theaddress of the wireless relay communication terminal 203 is comparedwith the address of the final relay terminal (Relay DA) extracted fromthe Address 3 field of the relay frame. If the two addresses aredifferent, it is determined to update the address in the Address 3field. If the two addresses match (if the address in the Address 3 fieldis not to be updated), the process advances to step S7.

If YES in step S23, the process advances to step S5, and the address ofthe wireless relay communication terminal (in this case, the wirelessrelay communication terminal 203) registered in the address table of thewireless relay communication terminal 202 and connected to the wirelesscommunication terminal 103 as the DA is determined as a new address tobe inserted into the Address 3 field, instead of the MAC address of thewireless relay communication terminal presently set in the Address 3field.

Note that in this example, the address of the final wireless relaycommunication terminal inserted by the wireless relay communicationterminal 201 is the address of the wireless relay communication terminal203, and the wireless communication terminal 103 as the finaldestination terminal is connected to the wireless relay communicationterminal 203, so it is unnecessary to update the address of the finalwireless relay communication terminal inserted by the wireless relaycommunication terminal 201. Accordingly, the process advances from stepS23 to step S7 to transmit the relay frame shown in the row b in FIG. 10as in the second embodiment.

The case where it is necessary to correct the address of a finalwireless relay communication terminal will be explained below withreference to FIG. 13.

Assume that the wireless communication terminal 101 transmits data whosefinal destination is the wireless communication terminal 103 in FIG. 13.When the wireless relay communication terminal 201 transmits a relayframe to the wireless relay communication terminal 202, the wirelesscommunication terminal 103 as the final destination terminal isconnected to the wireless relay communication terminal 203. Therefore,the wireless relay communication terminal 201 transmits the relay frameshown in the row a in FIG. 10 to the wireless relay communicationterminal 202.

The wireless relay communication terminal 202 having received this relayframe checks the routing information in step S23 to find a wirelessrelay communication terminal to which the wireless communicationterminal 103 as the DA is connected. At this point, the wirelesscommunication terminal 103 is already connected to another wirelessrelay communication terminal 205, and information indicating that thewireless relay communication terminal 203 is connected to the wirelessrelay communication terminal 205 and the wireless communication terminal103 is connected to the wireless relay communication terminal 205 isregistered in the address table of the wireless relay communicationterminal 202. Accordingly, the wireless relay communication terminal 202corrects the address of a final wireless relay communication terminal inthe received relay frame from the address of the wireless relaycommunication terminal 203 to that of the wireless relay communicationterminal 205 (step S5).

That is, as shown in a row a in FIG. 14, the wireless relaycommunication terminal 202 transmits a relay frame in which ToDS=1,FromDS=1, AE=1, the Address 1 field contains the MAC address of thewireless relay communication terminal 203, the Address 2 field containsthe MAC address of the wireless relay communication terminal 202, theAddress 3 field contains the MAC address of the wireless relaycommunication terminal 205, the Address 4 field contains the MAC addressof the wireless relay communication terminal 201, the Address 5 fieldcontains the MAC address of the wireless communication terminal 103, andthe Address 6 field contains the MAC address of the wirelesscommunication terminal 101.

Note that the wireless relay communication terminal 202 is not directlywirelessly connected to the wireless relay communication terminal 205.If they are directly connected, however, as shown in FIG. 14( b), arelay frame in which the Address 1 field contains the MAC address of thewireless relay communication terminal 205 is transmitted.

The event as shown in FIG. 13 occurs in, e.g., the following case. If awireless relay communication terminal is a power saving terminal and hasnot received routing information because the terminal was in a sleepstate when the routing information was updated on a wireless relaysystem, the terminal uses the routing information older than that ofanother wireless relay communication terminal on the wireless relaysystem when transmitting a relay frame. In addition, if the wirelesscommunication terminal 103 shown in FIG. 13 changes the connection fromthe wireless relay communication terminal 203 to the wireless relaycommunication terminal 205 immediately after a relay frame istransmitted to the next wireless relay communication terminal (i.e.,reassociation with the wireless relay communication terminal 205 in theIEEE802.11 wireless LAN system), the routing information cannot beupdated in time for transmission of the relay frame on the wirelessrelay system. As a consequence, the relay frame is transmitted by usingthe old routing information.

Note that this embodiment is not limited to the process sequence shownin the flowchart of FIG. 12. It is only necessary to be able to finallycorrect the address of a final wireless relay communication terminal ina relay frame received by a wireless relay communication terminal to anew address.

In the third embodiment as described above, a second wireless relaycommunication terminal having received a relay frame which istransmitted from a first wireless relay communication terminal and inwhich the address of a final wireless relay communication terminal isset in an address field for the address of a final wireless relaycommunication terminal corrects the address of the final wireless relaycommunication terminal to a new address.

If the second wireless relay communication terminal determines in stepS23 of FIG. 12 to update the address of the final wireless relaycommunication terminal in the received relay frame, the routinginformation (e.g., the final destination DA, the address of the finalwireless relay communication terminal connecting a communicationterminal corresponding to the DA, and the addresses of wireless relaycommunication terminals existing from the final wireless relaycommunication terminal to the wireless relay communication terminalhaving received the frame, or at least the address of the final wirelessrelay communication terminal) in the address table stored in the addresstable storage unit 14 of the second wireless relay communicationterminal may also be transmitted to the first wireless relaycommunication terminal having transmitted the relay frame.

(Effects)

In the third embodiment described above, if the address of a finalwireless relay communication terminal in a received relay frame differsfrom the address of a final wireless relay communication terminal heldin a wireless relay communication terminal having received the frame(e.g., if the address of the final wireless relay communication terminalheld in the wireless relay communication terminal having received theframe is newer than the address of the final wireless relaycommunication terminal set in the received relay frame), the wirelessrelay communication terminal having received the frame updates theaddress in a field prepared for the final wireless relay communicationterminal of the relay frame with the address of the final wireless relaycommunication terminal held in the wireless relay communication terminalhaving received the frame, and transmits the obtained frame as a relayframe. Consequently, even if the routing information in the addresstable of the transmission source of the relay frame is old, eachwireless relay communication terminal before the final destinationrelays the frame after updating the address of the final wireless relaycommunication terminal in accordance with the newest routinginformation. Accordingly, the relay frame can be delivered to acommunication terminal at the final destination.

Also, since each wireless relay communication terminal via which theframe is relayed before arriving at the final destination communicationterminal checks the routing information, the relay information can beappropriately updated. In addition, the relay function can beimplemented even in a situation in which a wireless relay communicationterminal holding old routing information (e.g., a power saving relayterminal) exists.

Furthermore, when a wireless relay communication terminal havingreceived a relay frame updates the address in a field prepared in therelay frame for the address of a final wireless relay communicationterminal, the wireless relay communication terminal having received theframe transmits routing information used in the update to a wirelessrelay communication terminal as the direct transmission source of thereceived relay frame. This makes it possible to efficiently notify newerrouting information to the wireless relay communication terminal as thedirect transmission source of the relay frame. Therefore, the relayfunction can be implemented even in a situation in which a wirelessrelay communication terminal holding old routing information (e.g., apower saving relay terminal) exists.

FOURTH EMBODIMENT

FIG. 15 is a flowchart for explaining the operation of a wireless relaycommunication terminal according to the fourth embodiment. FIG. 15 showsthe operation of the transmission/reception controller 13 when thewireless relay communication terminal receives a frame and transmitsinternally generated data. Note that the same reference numerals as inFIGS. 8, 9, and 12 denote the same portions in FIG. 15, and differentportions will be mainly explained below.

Step S22 in FIG. 12 (the process of checking whether the address in anaddress field describing the address of a final wireless relaycommunication terminal (e.g., the Address 3 field in this case) in areceived frame matches the address of a wireless relay communicationterminal having received the frame) is deleted from FIG. 15. That is, inFIG. 15, if it is determined in step S21 that the received frame is arelay frame including the six address fields, the process immediatelyadvances to step S23 to determine whether to update the address of afinal wireless relay communication terminal in the received relay frame.

Similarly to the third embodiment, if it is determined in step S23 toupdate the address of the final wireless relay communication terminal inthe Address 3 field of the received relay frame, the process advances tostep S5 to determine the new address of the final wireless relaycommunication terminal as the address to be inserted into the Address 3field. Then, the process advances to step S7 to generate a MAC header ofa relay frame and to transmit it onto the wireless medium (step S9) inthe same manner as described previously. For example, it is determinedto update the address if the address in a field prepared in the relayframe for the address of a final wireless relay communication terminaldiffers from the address of a final wireless relay communicationterminal obtained from the routing information held in the wirelessrelay communication terminal having received the frame. It is alsopossible to determine to update the address if the address of the finalwireless relay communication terminal obtained from the routinginformation held in the wireless relay communication terminal havingreceived the frame is newer than the address in the field prepared inthe relay frame for the address of the final wireless relaycommunication terminal.

If it is determined in step S23 not to update the address in the Address3 field, the process advances to step S3.

Similarly to the first embodiment, if it is determined in step S3 byreferring to the address table that a wireless communication terminal atthe final destination DA in the received frame is connected to thewireless relay communication terminal having received the frame, theprocess advances to step S8 to generate a MAC header not including theRelay Header field shown in FIG. 4. After that, the process advances tothe wireless transmission process in step S9.

If it is determined in step S3 that the communication terminal at thefinal destination DA is not connected to the wireless relaycommunication terminal having received the frame, the process advancesto step S4.

If a final wireless relay communication terminal can be determined forthe final destination (DA) in step S4, the MAC address of this finalwireless relay communication terminal is selected as the address to beinserted into the Address 3 field (step S5). Then, a MAC headerincluding the Relay Header field as shown in FIG. 4 is generated (stepS7), and the wireless transmission process is performed in step S9.

If no final wireless relay communication terminal can be determined instep S4, the address of a wireless relay communication terminal selectedas the direct transmission destination of the relay frame from thewireless relay communication terminals registered in the address tableand connected to the wireless relay communication terminal havingreceived the frame, is also selected as the address to be inserted intothe Address 3 field (step S6). Then, a MAC header as shown in the row ein FIG. 7 is generated (step S7), and a transmission frame is generatedand transmitted onto the wireless medium (step S9).

Note that in step S4 of this embodiment, it is determined that theaddress of the final wireless relay communication terminal can bedetermined if the Address 3 field of the received frame contains not theaddress of the wireless relay communication terminal having received theframe, but the address of an arbitrary wireless relay communicationterminal.

Note also that this embodiment is not limited to the process sequenceshown in the flowchart of FIG. 15. It is only necessary to be able tocorrect the address of a final wireless relay communication terminal ina relay frame received by a wireless relay communication terminal to anew address.

(Effects)

In the above fourth embodiment, if the address in a field prepared in arelay frame for the address of a final wireless relay communicationterminal differs from the address of a final wireless relaycommunication terminal obtained from routing information held in awireless relay communication terminal having received the frame(furthermore, if, for example, the address of the final wireless relaycommunication terminal obtained from the routing information held in thewireless relay communication terminal having received the frame is newerthan the address in the field), the wireless relay communicationterminal having received the frame updates the address in the field ofthe relay frame with the address of the final wireless relaycommunication terminal selected by the wireless relay communicationterminal having received the frame, and transmits the frame as a relayframe. Consequently, even if the routing information on the addresstable of the transmission source of the relay frame is old, eachwireless relay communication terminal before the final destination canrelay the frame after updating the address of the final wireless relaycommunication terminal in accordance with the newest routinginformation. Accordingly, the relay frame can be delivered to thewireless communication terminal at the final destination.

Also, since each wireless relay communication terminal via which theframe is relayed before arriving at the final destination communicationterminal checks the routing information, the relay information can beappropriately updated. In addition, the relay function can beimplemented even in a situation in which a wireless relay communicationterminal holding old routing information (e.g., a power saving relayterminal) exists.

FIFTH EMBODIMENT

The fifth embodiment will principally explain differences from the firstto fourth embodiments. This embodiment differs from the first to fourthembodiments in that if no final wireless relay communication terminalcan be determined, a specific value is set instead of the directtransmission destination address (RA) as the value of the Address 3field in the MAC header of a relay frame.

FIG. 16 is a flowchart for explaining the operation of a wireless relaycommunication terminal according to the fifth embodiment. FIG. 16 showsthe operation of the transmission/reception controller 13 when thewireless relay communication terminal receives a frame and transmitsinternally generated data. Note that the same reference numerals as inFIG. 8 denote the same portions in FIG. 16, and different portions willbe mainly explained below.

That is, step S6 in FIG. 8 is replaced with step S31 in FIG. 16. In stepS6 of FIG. 8, if the wireless relay communication terminal cannotdetermine the final wireless relay communication terminal (NO in stepS4), the address of the direct transmission destination (RA) is insertedinto the Address 3 field for the address of the final wireless relaycommunication terminal in the relay frame. In step S31 of FIG. 16,however, if the wireless relay communication terminal cannot determinethe final wireless relay communication terminal (NO in step S4), apredetermined value (specific value) is inserted into the Address 3field.

Note that it is also possible to replace step S6 in FIG. 15 with stepS31 in FIG. 16.

Furthermore, as shown in FIGS. 17 and 18, step S6 in FIGS. 9 and 12 mayalso be replaced with step S31 in FIG. 16. In this case, step S22 inFIGS. 9 and 12 are replaced with step S32 as shown in FIGS. 17 and 18.In step S32, whether the Address 3 field of a received frame containsthe specific value is checked.

Referring to FIG. 16, if a communication terminal at the finaldestination in the received frame is not connected to the wireless relaycommunication terminal having received the frame (NO in step S3), theprocess advances to step S4. If no final wireless relay communicationterminal can be determined (NO in step S4), a predetermined value(specific value) is inserted into the Address 3 field. However, thepresent invention is not limited to this case.

For example, as shown in FIG. 19, if the communication terminal at thefinal destination in the received frame is not connected to the wirelessrelay communication terminal having received the frame (NO in step S3),the process advances to step S32 to check whether the specific value isset in the Address 3 field of the received frame. If the specific valueis set, the process advances to step S4 to check whether the finalwireless relay communication terminal can be determined. If the finalwireless relay communication terminal can be determined, the processadvances to step S5; if not, the process advances to step S7. If it isdetermined in step S32 that the specific value is not set in the Address3 field of the received frame, the process directly advances to step S7.

Also, as shown in FIG. 20, for example, if NO in step S3, the processadvances to step S32 to check whether the specific value is set in theAddress 3 field of the received frame. If the specific value is set,whether the final wireless relay communication terminal can bedetermined is checked in step S4. If the final wireless relaycommunication terminal can be determined, the process advances to stepS5; if not, the process advances to step S7. If it is determined in stepS32 that the specific value is not set in the Address 3 field of thereceived frame, the process advances to step S23 to check whether theaddress in the Address 3 field can be updated. If it is determined thatthe address can be updated, the process advances to step S5; if not, theprocess advances to step S7.

Furthermore, as shown in FIG. 21, for example, if NO in step S3, theprocess advances to step S21 to check whether the frame includes the sixaddress fields (the Address 1, 2, 3, and 4 fields shown in FIG. 4 andthe Address 5 and 6 fields shown in FIG. 6). If the received frameincludes the six address fields, the process advances to step S32; ifnot, the process advances to step S4. If it is determined in step S32that the specific value is not set in the Address 3 field of thereceived frame, the process advances to step S7. If it is determined instep S32 that the specific value is set in the Address 3 field of thereceived frame, the process advances to step S4.

The specific value is, e.g., a specific value designated by a wirelessrelay system. This specific value designated by a wireless relay systemcan be a specific value defined by a standard or a large-frame systemusing a certain mechanism, or a specific value unique to each wirelessrelay system operating on the basis of the standard or the large-framesystem using the mechanism. A large-frame system using a certainmechanism is a system not based on a standard but comprising productsuniquely produced in order to implement a wireless relay system.

For example, the use of a specific value designated by a certain generalwireless relay system will be explained below with reference to FIG. 22.The definition of IEEE Std 802-2001 has the following limitations onaddress fields.

Referring to FIG. 22, each address field comprises a bit string havingsix octets, i.e., six bytes. Although octets from the third octet(Octet: 2) to the fifth octet (Octet: 4) are omitted from FIG. 22, eachoctet comprises eight bits each of which is “0” or “1”.

In FIG. 22, LSB (Least Significant Bit) is the lowermost bit, MSB (MostSignificant Bit) is the uppermost bit in an octet, and the first twobits, i.e., the LSB and the next bit, of the first octet arerespectively called an I/G (Individual/Group) bit and a U/L(Universal/Local) bit.

The I/G bit is also represented by an I/G address bit. Including anaddress of the IEEE802.11 wireless LAN system, the I/G bit is set to “1”for a multicast (including broadcast) address and “0” for a unicastaddress for designating the address of a unique communication terminal.

The U/L bit is also represented by a U/L address bit. For an addressused in the IEEE802.11 wireless LAN system, the U/L bit is set to “1” asa local address.

In the IEEE802.11 wireless LAN system, all of the bits are “1” in thebroadcast address.

On the basis of the above limitations, a value in which the U/L bit is“1” and all the other bits are “0” can be used as the specific value. Itis also possible to respectively set “0” and “1” as the I/G bit and theU/L bit (i.e., the first two bits are “01”), and insert a value uniquelydesignated by the wireless relay system into the remaining 46 bits.Alternatively, since the U/L bit need only be “1” in IEEE802.11, it ispossible to set “1” as both the I/G bit and the U/L bit (i.e., the firsttwo bits are “11”), and insert a value uniquely designated by thewireless relay system into the remaining 46 bits. In this case, as thespecific value to be used, it is necessary to select at least a valuethat is not allocated as a specific multicast MAC address in thewireless relay system. This specific value can be inserted as a relaysystem ID (IDentifier) into the Address 3 field for designating theaddress of a final wireless relay communication terminal in the MACheader of a relay frame if the final wireless relay communicationterminal cannot be determined. The specific value can also be used toidentify wireless relay systems existing in the same area or inpartially overlapped areas.

A wireless relay communication terminal having received the relay framecan know that the final wireless relay communication terminal could notbe determined by the wireless relay communication terminal thattransmitted the relay frame by detecting that the specific value is setas the final wireless relay communication terminal address of thereceived relay frame in, e.g., step S32 of the flowchart shown in FIG.17. If the wireless relay communication terminal having received therelay frame can determine the address of the final wireless relaycommunication terminal (YES in step S4), the wireless relaycommunication terminal continues data relay by transmitting a frame inwhich the Address 3 field is rewritten, i.e., the address information inthe MAC header is updated (steps S5, S7, and S9).

(Effects)

In the above fifth embodiment, if the transmission source of a relayframe cannot determine the address of a final wireless relaycommunication terminal, a predetermined specific value indicating thisinformation is described in a field prepared for the address of thefinal wireless relay communication terminal (e.g., the Address 3 field).Accordingly, wireless relay communication terminals participating indata relay can readily detect that the field requires update, and any ofthese wireless relay communication terminals before the final wirelessrelay communication terminal inserts the address of the final wirelessrelay communication terminal into the field. Even when the relay frameis transmitted while the routing information of the final destination isundetermined, frame relay can be continued to the final destination viathe final wireless relay communication terminal.

SIXTH EMBODIMENT

In the sixth embodiment, a method of generating a specific value uniqueto a wireless relay system explained in the fifth embodiment will beexplained.

The fifth embodiment has explained the method that uses, as a specificvalue unique to a wireless relay system and used when a final wirelessrelay communication terminal cannot be determined, a value in which theI/G bit and the U/L bit are respectively “0” and “1” (i.e., the firsttwo bits are “01”) or both the I/G bit and the U/L bit are “1” (i.e.,the first two bits are “11”) in FIG. 22 and the remaining 46 bits have avalue uniquely designated by the wireless relay system. In the sixthembodiment, a method of determining the 46-bit data will be explained.

This 46-bit data is generated from, e.g., a random number generated by awireless relay communication terminal having started the wireless relaysystem. To execute CSMA/CA (Carrier Sense Multiple Access with CollisionAvoidance) in the IEEE802.11 wireless LAN system, when it is detectedthat the wireless medium is idle (i.e., the medium has no transmissionor is not reserved by virtual carrier sense), during the idle period,each wireless communication terminal waits for a fixed time length(Inter-Frame Space: IFS). After further waiting for the length of thenumber of slots designated by a randomly generated number (i.e., afterperforming random backoff), the wireless communication terminaltransmits data. If the wireless medium becomes busy, the number of slotsremaining in random backoff is held. After the wireless medium isdetected to be idle again, the wireless communication terminal waits forthe IFS period and resumes counting down the number of slots remainingin the random backoff procedure. When the number of slots reaches “0”,the wireless communication terminal transmits data.

A random number generator for generating a random number to perform thisrandom backoff is included in the wireless communication terminal, e.g.,in the transmission/reception controller 13 shown in FIG. 2. It ispossible to generate a 46-bit random number by using this random numbergenerator, and add two bits, i.e., “0” as the I/G bit and “1” as the U/Lbit to this random number, thereby obtaining a specific value unique toa wireless relay system.

A specific value unique to a wireless relay system may also be obtainedby generating 46 bits by converting a code (e.g., the ASCII charactercode) input by a user via a user interface, and adding two bits, i.e.,“0” as the I/G bit and “1” as the U/L bit to the 46 bits.

The specific value unique to the wireless relay system generated asdescribed above is notified to another wireless relay communicationterminal on the wireless relay system during the process of, e.g.,constructing the wireless relay system. In this manner, this specificvalue can be used as a specific value to be inserted when each wirelessrelay communication terminal on the wireless relay system cannotdetermine the final wireless relay communication terminal.

The specific value can be notified to the whole wireless relay system bya method in which a wireless relay communication terminal havinggenerated the specific value broadcast the specific value, and anotherwireless relay communication terminal having received the specific valuefurther broadcast the specific value. As a method of broadcasting thespecific value, for example, the specific value is inserted into amanagement frame whose RA is set to a broadcast address consisting ofall “1”s and transmitted. The method of notifying the specific value tothe whole wireless relay system may also be based on a method ofrelaying a data frame whose DA is the broadcast address in theconventional wireless relay system.

(Effects)

The above sixth embodiment has exemplified the method by which any ofwireless relay communication terminals constructing a wireless relaysystem generates a specific value to be set in a field prepared in arelay frame for the address of a final wireless relay communicationterminal, if the address of the final wireless relay communicationterminal cannot be determined, by generating a 46-bit random numbervalue and prefixing “10” to this random number value. The wireless relaycommunication terminal having generated this specific value notifies thewireless relay system of the generated specific value, thereby readilynotifying all the wireless relay communication terminals in the wirelessrelay system of the specific value.

SEVENTH EMBODIMENT

In the seventh embodiment, when transmitting a relay frame, the wirelessrelay communication terminal explained in any of the first to sixthembodiments described above inserts, into the relay frame, information(update information) concerning the routing information on the addresstable (stored in the address table storage unit 14) used whentransmitting the relay frame.

This update information is inserted into, e.g., the Relay Control fieldbefore the Address 5 field in the Relay Header field shown in FIG. 6. Itis also possible to add a new field after the Address 6 field shown inFIG. 6, and insert the update information into this new field.

In a wireless relay system in which wireless relay communicationterminals share, periodically check, and update the routing informationfor delivering data to communication terminals connected to the wirelessrelay communication terminals and having no relay function, the updateinformation is, e.g., the number of updated times of the routinginformation (address table).

To share the updated new routing information on the wireless relaysystem, a wireless relay communication terminal having updated therouting information broadcasts the new routing information, and anotherwireless relay communication terminal having received the new routinginformation broadcasts the new routing information, thereby the wholewireless relay system can be notified of the new routing information. Tobroadcast the new routing information, the new routing information isinserted into a management frame whose RA is set to a broadcast addressconsisting of all “1”s.

The method of notifying the whole wireless relay system of the newrouting information may also be based on a method of relaying a dataframe whose DA is the broadcast address in the conventional wirelessrelay system.

Each wireless relay communication terminal stores an address table andupdate information of the address table in the address table storageunit 14.

A wireless relay communication terminal having received a relay frameincluding the update information uses the update information in therelay frame to compare the update information of the routing informationstored in the address table storage unit 14 of the wireless relaycommunication terminal having received the relay frame with the updateinformation of the routing information used by a wireless relaycommunication terminal as the transmission source of the relay frame,thereby checking which routing information is newer.

For example, in step S23 of FIG. 12 explained in the third embodiment orin step S23 of FIG. 15 explained in the fourth embodiment, the updateinformation in a received relay frame is used to determine whether theaddress of a final wireless relay communication terminal in the Address3 field of the relay frame is newer than that of a final wireless relaycommunication terminal contained in routing information on the addresstable of a wireless relay communication terminal having received therelay frame.

If the update information of the routing information stored in thewireless relay communication terminal having received the relay frame isnewer than that of the routing information used by a wireless relaycommunication terminal as the transmission source of the relay frame, itis determined that the routing information can be updated.

In another case, the update information may be an updated time. Theupdated time may be a time at which the routing information is updatedor a time at which notification of the updated routing information tothe wireless relay system is started. As the updated time, it ispossible to use the timer value of the timer 15 (a TSF (TimingSynchronization Function) timer in IEEE802.11) formed in thetransmission/reception controller 13 of a wireless relay communicationterminal that starts notification of the updated new routinginformation. In this case, it is only necessary to be able to checkwhether the time information is new or old. Therefore, only a limitednumber of digits at the end of the TSF timer value may be used.

As a method of synchronizing the timers of wireless relay communicationterminals, it is possible to use the method of synchronizing the TSFtimers of wireless communication terminals in the conventional 802.11IBSS (ad-hoc) configuration. Alternatively, a wireless relaycommunication terminal having started a wireless relay communicationsystem may play the role of a wireless communication base station in theinfrastructure BSS configuration, and notify the TSF timer value. Inthis case other wireless relay communication terminals function aswireless communication terminals connecting to the wirelesscommunication base station and acquiring and synchronizing with the TSFtimer value notified by the wireless communication base station.

In step S23 of FIG. 12 explained in the third embodiment or in step S23of FIG. 15 explained in the fourth embodiment, if the update informationof the routing information stored in a wireless relay communicationterminal having received a relay frame is found to be newer than that ofthe routing information used by a wireless relay communication terminalas the transmission source of the relay frame, the wireless relaycommunication terminal having received the relay frame may notify thewireless relay communication terminal as the relay frame transmissionsource of the routing information stored in the address table storageunit 14 of the wireless relay communication terminal having received therelay frame.

On the other hand, in step S23 of FIG. 12 explained in the thirdembodiment or in step S23 of FIG. 15 explained in the fourth embodiment,if the update information of the routing information stored in awireless relay communication terminal having received a relay frame isfound to be older than that of the routing information used by awireless relay communication terminal as the transmission source of therelay frame (if the latter is found to be newer than the former), thewireless relay communication terminal having received the relay framemay also transmit, to the wireless relay communication terminal as thetransmission source of the relay frame, a request frame of requestingtransmission of the routing information stored in the address tablestorage unit 14 of the wireless relay communication terminal as therelay frame transmission source. This request frame is transmitted as amanagement frame in, e.g., the IEEE802.11 wireless LAN system. Awireless relay communication terminal having received the request frametransmits, as a response frame, a management frame including the routinginformation held in the wireless relay communication terminal to awireless relay communication terminal as the transmission source of therequest frame.

(Effects)

In the above seventh embodiment, a wireless relay communication terminalcompares the update information of the address of a final wireless relaycommunication terminal in a received relay frame with the updateinformation of an address table held in the wireless relay communicationterminal and containing the address of the final wireless relaycommunication terminal. Therefore, if, for example, the address of thefinal wireless relay communication terminal held in the wireless relaycommunication terminal having received the frame differs from that ofthe final wireless relay communication terminal in the received relayframe in step S23 of FIG. 12 or 15 explained in the third or fourthembodiment, it is possible to easily determine which address is newer.

If the address of the final wireless relay communication terminal heldin the wireless relay communication terminal having received the frameis newer than that of the final wireless relay communication terminal inthe received relay frame, the wireless relay communication terminalupdates the address in a field prepared in the relay frame for the finalwireless relay communication terminal with the address of the finalwireless relay communication terminal held in the wireless relaycommunication terminal, and transmits the updated frame as a relayframe. Consequently, even when the routing information on the addresstable of the transmission source of a relay frame is old, a wirelessrelay communication terminal before the final destination can relay theframe after updating the address of a final wireless relay communicationterminal in accordance with the newest routing information. Accordingly,the relay frame can be delivered to a wireless communication terminal atthe final destination.

Also, when a wireless relay communication terminal having received arelay frame updates the address in a field prepared in the relay framefor the address of a final wireless relay communication terminal, thewireless relay communication terminal transmits the routing informationused in the update to a wireless relay communication terminal as thedirect transmission source of the received relay frame. Consequently,the wireless relay communication terminal as the direct transmissionsource of the relay frame can be efficiently notified of newer routinginformation.

Furthermore, if the address of a final wireless relay communicationterminal held in a wireless relay communication terminal having receiveda relay frame is older than the address of a final wireless relaycommunication terminal in the received relay frame (although thewireless relay communication terminal having received the relay framedoes not update the address in a field prepared in the relay frame todescribe the address of the final wireless relay communicationterminal), the wireless relay communication terminal transmits, to awireless relay communication terminal as the direct transmission sourceof the relay frame, a request frame of requesting transmission of theaddress table (routing information) held in the wireless relaycommunication terminal as the direct transmission source of the relayframe. In this manner, the wireless relay communication terminal havingreceived the relay frame can acquire newer routing information from aresponse frame from the wireless relay communication terminal as thedirect transmission source of the relay frame.

As described above, the relay function can be readily implemented evenin a situation in which a wireless relay communication terminal holdingold routing information (e.g., a power saving relay terminal) exists.

Eighth Embodiment

In the eighth embodiment, when transmitting a relay frame, the wirelessrelay communication terminal explained in any of the first to seventhembodiments described above inserts, into this relay frame, dataidentification information for identifying congestion data (congestiondata identification information) and information for limiting the numberof times of relay (relay control information).

Congestion is a phenomenon in which identical data arrive at the samewireless communication terminal through different routes. In some cases,the same data is transmitted to the same wireless communication terminala number of times. Data arriving at the same wireless communicationterminal a number of times is called congestion data.

The congestion data identification information and the relay controlinformation are inserted into, e.g., the Relay Control field before theAddress 5 field in the Relay Header portion shown in FIG. 6. It is alsopossible to add a new field after the Address 6 field shown in FIG. 6,and insert the information in this new field.

The congestion data identification information is, e.g., a sequencenumber that is unique to the data generation source and monotonicallyincreases. Each wireless relay communication terminal determines whetherdata in a received relay frame is already relayed, on the basis of theSA and the sequence number of the relay frame. If the data in thereceived relay frame is already relayed, the received relay frame isdiscarded. This makes it possible to prevent congestion data fromoverflowing onto the wireless relay system.

The relay control information for limiting the number of times of relayis a maximum number of times allocated for relay (a maximum number oftimes of multi-hop) determined by, e.g., the data generation source orthe first wireless relay communication terminal (Relay SA) of the datarelay. The value of the number of times of relay is reduced by onewhenever a relay frame containing the data is relayed by a wirelessrelay communication terminal. If a wireless relay communication terminalhas received a relay frame in which the value of the number of times ofrelay is “0”, this wireless relay communication terminal does not relaythe relay frame to any other wireless relay communication terminal (doesnot transmit the relay frame).

In this case, if a wireless relay communication terminal having receiveda frame containing the relay control information is connected to awireless communication terminal at the final destination of the frame,this wireless relay communication terminal may transmit a non-relayframe to the wireless communication terminal even when the value of thenumber of times of relay is “0” through, e.g., steps S3 and S8 of FIG.8. That is, the relay control information limits the number of times oftransmission of a relay frame.

Contrary to the above example, it is also possible to determine amaximum number of times of relay in the wireless relay system, and usethe number of actually relayed times as the relay control information.In this case, the maximum number of times of relay can be a valuedefined by a standard or a large-frame system using a certain mechanism,or a value unique to each wireless relay system operating on the basisof the standard or the large-frame system using the mechanism. Todetermine and use a maximum number of times of relay unique to eachwireless relay system, for example, a wireless relay communicationterminal having started the wireless relay system determines the maximumnumber of times of relay, and notifies another wireless relaycommunication terminal on the wireless relay system of the value of themaximum number of times of relay while constructing the wireless relaysystem. The wireless relay communication terminal having generated thevalue of the maximum number of times of relay broadcasts the value.Another wireless relay communication terminal having received the valuefurther broadcasts the value, thereby the whole wireless relay system isnotified of the value. For example, the value of the maximum number oftimes of relay is inserted into a management frame whose RA is set to abroadcast address consisting of all “1”s, and broadcasted bytransmitting the frame. The value of the maximum number of times ofrelay may also be notified to the whole wireless relay system by using amethod of relaying a data frame whose DA is the broadcast address in theconventional wireless relay system.

The relay control information may be time information for limiting thelifetime (the time of existence) of data to be relayed, instead of thenumber of times of relay or its maximum value as described above. Inthis case, relay is stopped when the lifetime has expired. For example,the time at which data is generated in the data generation source, thetime at which the data is converted into a frame in the data generationsource, or the time at which the frame is stored in a transmission queuefor accessing a channel in the data generation source is inserted as therelay control information into the frame. As the time, it is possible touse, e.g., the timer value of the timer 15 (the TSF (TimingSynchronization Function) timer in the IEEE802.11 wireless LAN system)formed in the transmission/reception controller 13. The lifetime of datacan be a value defined by a standard or a large-frame system using acertain mechanism, or a value unique to each wireless relay systemoperating on the basis of the standard or the large-frame system usingthe mechanism. The lifetime length may also be changed in accordancewith the type of data.

As a method of determining and using the value of the lifetime unique toeach wireless relay system, it is possible to use the same procedure asthat for determining a maximum number of times of relay described above.The value of the lifetime may also be changed in accordance with thetype of traffic (TID (Traffic IDentifier) in the IEEE802.11 wireless LANsystem) or the type of access (AC (Access Category) in the IEEE802.11wireless LAN system). This makes it possible to limit unnecessary relayin accordance with the characteristics of traffic. A wireless relaycommunication terminal refers to the time contained as the relay controlinformation in a received relay frame, and compares the time with thetimer value of the timer 15 held in the wireless relay communicationterminal. If the difference between the timer value and the time of therelay control information has exceeded a predetermined lifetime length,the wireless relay communication terminal does not relay data in therelay frame (does not retransmit the data onto the wireless medium).

(Effects)

By thus describing the congestion data identification information andthe relay control information in a frame, it is possible to preventcongestion data from overflowing on a wireless relay system, suppressthe waste of wireless resources (e.g., the wireless medium occupationtime) caused by transmission of the congestion data, and suppress theincrease in power consumption of a wireless communication terminal,particularly, a wireless relay communication terminal, caused bytransmission/reception of the congestion data.

As explained above, when performing multi-hop communication thatforwards data to a communication terminal at the final destination viawireless relay communication terminals, each of the above embodimentsmakes data relay possible even if the address of a final wireless relaycommunication terminal connecting the communication terminal at thefinal destination is undetermined, or the data is forwarded via awireless relay communication terminal holding old routing information(e.g., a power saving wireless relay communication terminal).

1. A wireless communication apparatus having a relay function,comprising: a memory to store an address of a first wirelesscommunication apparatus connected to the wireless communicationapparatus and having a relay function; and a first transmitting unitconfigured to transmit a first relay frame addressed to the firstwireless communication apparatus, the first relay frame including (a) afirst address field prepared for a final destination address, an addressof a second communication apparatus not connected to the wirelesscommunication apparatus being set in the first address field, and (b) asecond address field prepared for an address of a third wirelesscommunication apparatus connecting the second communication apparatusand having a relay function, one of an address except for the address ofthe third wireless communication apparatus and a specific value beingset in the second address field.
 2. The apparatus according to claim 1,wherein the memory stores addresses of a plurality of communicationapparatuses including the first wireless communication apparatus, andthe first transmitting unit transmits the first relay frame when theaddress of the third wireless communication apparatus is not stored inthe memory.
 3. The apparatus according to claim 2, further comprising asecond transmitting unit configured to transmit, when the address of thethird wireless communication apparatus is stored in the memory, a secondrelay frame including (a) the first address field in which the addressof the second communication apparatus is set, and (b) the second addressfield in which the address of the third wireless communication apparatusis set.
 4. The apparatus according to claim 1, wherein the addressexcept for the address of the third wireless communication apparatus isthe address of the first wireless communication apparatus.
 5. Theapparatus according to claim 1, wherein first two bits of the specificvalue are one of “01” and “11”.
 6. The apparatus according to claim 1,wherein the specific value is 48-bit data, first two bits of thespecific value are one of “01” and “11”, and 46 bits following the firsttwo bits have an arbitrary value.
 7. The apparatus according to claim 6,wherein the 46 bits are randomly generated.
 8. The apparatus accordingto claim 2, further comprises a receiving unit configured to receive aframe including the first address field in which the address of thesecond communication apparatus is set, and wherein the firsttransmitting unit transmits, when the receiving unit receives the frameand the address of the third wireless communication apparatus connectingthe second communication apparatus is not stored in the memory, thefirst relay frame including a frame body of the frame received by thereceiving unit.
 9. The apparatus according to claim 8, wherein the framereceived by the receiving unit includes the second address field inwhich one of the address of the wireless communication apparatus and thespecific value is described.
 10. The apparatus according to claim 3,further comprises a receiving unit configured to receive a frameincluding the first address field in which the address of the secondcommunication apparatus is set, and wherein the second transmitting unittransmits, when the receiving unit receives the frame and the address ofthe third wireless communication apparatus connecting the secondcommunication apparatus is stored in the memory, the second relay frameincluding (a) the second address field in which the address of the thirdwireless communication apparatus stored in the memory is set, and (b) aframe body of the frame received by the receiving unit.
 11. Theapparatus according to claim 10, wherein the frame received by thereceiving unit includes the second address field in which one of theaddress of the wireless communication apparatus and the specific valueis described.
 12. The apparatus according to claim 10, wherein the framereceived by the receiving unit includes the second address field, thememory stores the address of the third wireless communication apparatusconnecting the second communication apparatus, and the secondtransmitting unit transmits, when the address of the third wirelesscommunication apparatus stored in the memory differs from the addressset in the second address field of the frame received by the receivingunit, the second relay frame including the second address field in whichthe address of the third wireless communication apparatus stored in thememory is set.
 13. The apparatus according to claim 12, wherein thesecond transmitting unit transmits, when the address of the thirdwireless communication apparatus stored in the memory is newer than theaddress set in the second address field of the frame received by thereceiving unit, the second relay frame including the second addressfield in which the address of the third wireless communication apparatusstored in the memory is set.
 14. The apparatus according to claim 13,wherein the memory further stores update information of the addressstored in the memory, the frame received by the receiving unit furtherincludes update information of the address, and the second transmittingunit further includes a comparison unit configured to compare the updateinformation stored in the memory with the update information of theaddress in the third relay frame received by the receiving unit, todetermine whether the address of the third wireless communicationapparatus stored in the memory is newer than the address set in thesecond address field of the frame received by the receiving unit. 15.The apparatus according to claim 14, wherein the update information isone of the number of updated times and an updated time.
 16. Theapparatus according to claim 13, further comprising a third transmittingunit configured to transmit the information stored in the memory to afourth wireless communication apparatus which is a transmission sourceof the frame received by the receiving unit, when the address of thethird wireless communication apparatus stored in the memory is newerthan the address set in the second address field of the frame receivedby the receiving unit.
 17. The apparatus according to claim 8, whereinthe frame received by the receiving unit includes four address fieldsincluding the first address field, and the first relay frame includessix address fields including the four address fields, the second addressfield, and a third address field prepared for relay SA that is anaddress of a forwarding starting point.
 18. The apparatus according toclaim 17, wherein the frame received by the receiving unit includes sixaddress fields including the first address field, the second addressfield, and a third address field prepared for Relay SA that is anaddress of a forwarding starting point of the frame, and of the sixaddress fields in the first relay frame, at least the address in thefirst address field and the address in the third address field arerespectively the same as the address in the first address field and theaddress in the third address field of the frame received by thereceiving unit.
 19. A wireless communication method for a wirelesscommunication apparatus having a relay function, including: storing, ina memory, addresses of a plurality of communication apparatusesincluding a first wireless communication apparatus connected to thewireless communication apparatus and having a relay function;transmitting, when the address of the third wireless communicationapparatus is not stored in the memory, a first relay frame addressed tothe first wireless communication apparatus, the first relay frameincluding (a) a first address field prepared for a final destinationaddress, an address of a second communication apparatus not connected tothe wireless communication apparatus being set in the first addressfield, and (b) a second address field prepared for an address of a thirdwireless communication apparatus connecting the second communicationapparatus and having a relay function, one of an address except for theaddress of the third wireless communication apparatus and a specificvalue being set in the second address field; and transmitting, when theaddress of the third wireless communication apparatus is stored in thememory, a second relay frame including (a) the first address field inwhich the address of the second communication apparatus is set, and (b)the second address field in which the address of the third wirelesscommunication apparatus is set.
 20. A wireless communication method fora wireless communication apparatus having a relay function, including:storing, in a memory, addresses of a plurality of communicationapparatuses including a first wireless communication apparatus connectedto the wireless communication apparatus and having a relay function;receiving a frame, an address of a second communication apparatus notconnected to the wireless communication apparatus being set in a firstaddress field prepared in the frame for a final destination address;transmitting, when an address of a third wireless communicationapparatus connecting the second communication apparatus and having arelay function is not stored in the memory, a first relay frameaddressed to the first wireless communication apparatus, the first relayframe including (a) a frame body of the frame received by the receivingunit, (b) a first address field prepared for a final destinationaddress, the address of the second communication apparatus being set inthe first address field, and (c) a second address field prepared for theaddress of the third wireless communication apparatus, one of an addressexcept for the address of the third wireless communication apparatus anda specific value being set in the second address field; andtransmitting, when the address of the third wireless communicationapparatus is stored in the memory, a second relay frame including (a)the frame body of the frame received by the receiving unit, (b) thefirst address field in which the address of the second communicationapparatus being set, and (c) the second address field in which theaddress of the third wireless communication apparatus being set.